. >> reporter: but romney's running mate paul ryan downplayed the debate. >> i don't think one event will make or break the campaign. >> reporter: romney is trailing in the polls in most must-win states. tara mergener for cbs news, the white house. >>> in california, 10% of parents exempt their children from the mandatory school vaccinations. yesterday, governor brown signed a new law making vaccine waivers tougher to get. but a last-minute change is giving parents a new out. >> reporter: at tri-valley pediatrics, this 10-month-old is getting a flu shot. his mother talked to the doctor before making her decision. >> we definitely rely on our pediatrician as an expert. we put our son's health in his hands. >> reporter: a new california law aims to have more parents talking to their pediatrician before they are allowed to reject mandatory vaccines. >> overall, i think it's a step in the right direction. >> reporter: under current state law, before attending school or daycare, kids are required for certain vaccinations, and kids can opt out filing a personal belief exemption. this law d